Method of preparing a corrosion-resistant and ductile iron alloy with a high aluminum content

ABSTRACT

This invention involves a process of preparing a casting. The process includes preparing by known techniques a casting in accordance with the composition given below, but not containing the silicon component. The casting is brought to a temperature of the order of 1,600*C. The process continues with incorporation in the melt maintained at this temperature of an additive constituted on the one hand of at least one magnesium halide and on the other hand of powdered calcium. The slag is evaporated and the composition of the casting is completed by the addition of silicon. This invention also includes a casting having the following composition. Total carbon 1.4 to 2% Aluminium 8to 25% Silicon 1.8to 2.6% Manganese0.30% Iron (Remainder)

United States Patent n91 Renaud 1' Mar. 18, 1975 [76] Inventor: Henri Renaud, 15, Avenue Maunoury, 41 Mer, France [22] Filed: Feb. 4, 1972 [21] Appl. No.: 223,784

[30] Foreign Application Priority Data Feb. 4, 1971 France 71.04920 [52] US. Cl 75/53, 75/129, 75/130 R [51] Int. Cl. C2lc 7/00, C22c H02 [58] Field of Search... 75/129, 130, 130 R, 130 AB, 75/130 B, 53

[56] References Cited UNITED STATES PATENTS 2,048,824 7/1936 Simpson 75/129 2,119,521 7/1938 Brown 75/129 2,207,350 7/1940 Lorig 75/129 2,569,146 9/1951 Bolkcom 75/129 2,821,473 1/1958 Moore 75/130 AB 2,821,473 1/1958 Moore 75/130 2 847,296 8/1958 Hilty 75/129 2 855.336 10/1958 Curry 75/130 R 2 867,555 l/l959 Curry 75/130 R Kusaka 75/130 3,410,679 11/1968 Pardo 75/129 3,415,642 12/1968 Matsumoto 75/130 AB 3,415,642 12/1968 Matsumoto 75/130 Primary Examiner-L. Dewayne Rutledge Assistant E.\'aminer-Peter D. Rosenberg Attorney, Agent, or Firm-Christen & Sabol [57] ABSTRACT This invention involves a process of preparing a casting. The process includes preparing by known techniques a casting in accordance with the composition given below, but not containing the silicon component. The casting is brought to a temperature of the order of 1,600C. The process continues with incorporation in the melt maintained at this temperature of an additive constituted on the one hand of at least one magnesium halide and on the other hand of powdered calcium. The slag is evaporated and the composition of the casting is completed by the addition of silicon.

This invention also includes a casting having the following composition.

Total carbon 1.4 to 27! Aluminium 8 to 2571 Silicon 1.8 to 2.6% Manganese 0307! Iron (Remainder) 1 Claim, No Drawings METHOD OF PREPARING A CORROSION-RESISTANT AND DUCTILE IRON ALLOY WITH A HIGH ALUMINUM CONTENT The present invention relates to an alloyed, malleable casting, particularly an iron casting having a high aluminum content.

in the foundry art, white cast iron is known, which is without graphite and which is naturally hard and difficult to work; it is also difficult to mould.

Grey cast iron, which is richer in carbon, contains free graphite disseminated in the ferrite; it is fluid and may be worked more easily; it is more resistant to attack from chemical agents but offers only fairly low mechanical characteristics.

In practice, alloyed castings are most currently resorted to, particularly nickel castings with spheroidal graphite; however, these castings are more delicate to prepare and are of high cost price.

Aluminium castings are known which are particularly advantageous due to their high resistance to corrosion, but they do not enable the desired mechanical properties to be obtained. 7

The invention relates to a new aluminium casting composition which has the advantages of high resistance to corrosion and a much improved mechanical resistance.

The invention further relates to a process of preparing such a casting.

The invention has for an object, in the first place, a casting characterised by its chemical composition of the following formula:

Total carbon 1.4 to 2 7: Aluminium 8 to 7: Silicon 1.8 to 2.6 7: Manganese 0.30%

Iron (Remainder) This casting has an excellent resistance to corrosion and resists the action of chemical agents; it has an agreable appearance of polished silver; its mechanical qualities are very satisfactory and vary according to the content of aluminium within the following ranges:

R (tensile strength) 25 to 35 A (elongation) 2 to 6 E (limit of elasticity) 6 to 12 7:

In addition, the invention makes it possible to make a casting which has noteworthy physical qualities, a high resistance to corrosion, an agreable polished appearance and which benefits from a cost price much lower than that of nickel castings for equivalent or superior technical qualities and characteristics.

The invention further has for an object a process of preparing a casting in accordance with the above characteristics, enabling the physical and chemical qualities of the final product obtained to be further improved.

The process is characterised in that a casting is prepared by known techniques having the above composition, but not containing the silicon'component, this casting is taken to a temperature of the order of l,600C, and there is incorporated in the melt an additive constituted of two parts of at least one magnesium halide and one part of powdered calcium, the melt being completed by addition of silicon after the slag has been evacuated.

The process is described as follows. A pig iron is melted in a reverbatory furnace, an electric furnace or a cruible, said pig iron containing in percent (weight):

8 to 25 C 'l.5 to 2.5 Mg up to 0.3 Si up to 0.8- Fe (remainder Mg Fluoride 33% Mg Chloride 33% Ca (powder) 33% The total of the additive corresponds to an effective amount by weight of the final product.

The slag is removed from the molten metal by known process.

After about one hour the melt is completed by addition of silicon so that the total percent weight of silicon will be of 1.8 to 2.6 of the total product; to this end, ferrosilicon alloy ingots are incorporated in the molten iron.

Then the process is ended and the metal alloy is ready for casting into the moulds.

According to the invention, the additive added to the melt and maintained at 1,600C is preferably formed of:

/5; magnesium fluoride magnesIum chloride A; powdered calcium In the additve, the calcium acts as a nodularizing agent, and the Mg chloride is dissociated, and the Cl so-produced acts to purify the metal, whereas the Mg component is dissolved in the molten metal and helps the carbon to nodularize. The Mg fluoride is dissociated and since this reaction is an exothermic one, it raises the metal temperature; the Mg has the same action as above. The Mg coming from the additive is mostly destroyed in the process and eliminated with the slag, but its nodularizing action has been completed.

The addition of silicon in the proportion defined above is preferably effected in the form of an addition of ferrosilicon in the melt after a period of rest of the order of five minutes following the elimination of the slag.

The casting thus treated has improved characteristics, particularly an excellent resistance to corrosion; it may be easily moulded, machined or polished and conserves its polish in bad weather and in the presence of corrosive chemical agents.

Tests made by the Applicant have made it possible to assess the characteristics of the product obtained according to the formula and the process hereinabove, the characteristics being as follows:

R (tensile strength) 30 to 45 E (limit of elasticity) 18 to 35 A (elongation) 3 to 15 7c The casting may be prepared and treated as indicated hereinabove in an electric furnace, reverberatory furnace or crucible.

The casting according to the invention may be employed for moulding multiple pieces used in industry, building, household equipment, means of transport, and thus has an extremely wide field of application.

I claim:

1. Process of preparing a casting of an iron alloy with consisting of the following steps:

a. preparing an admixture having the composition:

total carbon 1.4 to 27:

4 e aluminum 8 to 25% manganese 0.307: iron (remainder) b. heating said admixture to a temperature in the order of l,600C, a melt having formed thereby: c. incorporating in said melt maintained at l,600C.

an additive composition formed of:

% magnesium fluoride /5 magnesium chloride and A of powdered calcium;

d. removing the slag from said melt;

e. completing the composition of said alloy by the addition of ferrosilicon in said melt after a period of rest of the order of five minutes following the removal of said slag; and

f. casting the melt to form said alloy. 

1. PROCESS OF PREPARING A CASTING OF AN IRON ALLOY WITH A HIGH ALUMINUM CONTENT WHICH HAS THE COMPOSITION: 